IL-15 was found to be a potent inducer of FoxP3 expression in CD4+ T cells and thus be more similar to IL-2 than IL-7 in that regard. IL-2,-7 and -15 were all shown to be potent inducers of CD4 and CD8 proliferation. The cytokine induced proliferation of CD4 cells was associated with CD25 expression while the proliferation of CD8 cells was not. IL-27 was shown to, at least partially, exert its anti-HIV effects throught the induction of pathways similar to those seen with interferon alpha. Patients with idiopathic CD4 lymphopenia were noted to be a heterogeneous group of patients some of whom have immune systems characterized by immune activation.